Heat exchanger

Abstract: The present invention is directed to a heat exchanger which includes an upper (11) and a lower (12) tank and a plurality of heat exchange units (13) extending between the upper and lower tanks. Each heat exchanger unit includes a plurality of plane portions (132) and a plurality of pipe portions (131), each having a longitudinal axis. The pipe portions are spaced from one another at about equal intervals and place the upper and lower tanks in fluid communication. Adjacent pipe portions are connected by the plane portions. The heat exchanger is provided with a plurality of louvers (133) formed in the plane portions along the longitudinal axis of the heat exchange unit. Each louver is formed by twisting a plane belt region which is defined between adjacent slits formed in the plane portions. A plane of each of the louvers is oriented to be substantially parallel to a plane which is perpendicular to the longitudinal axes of pipe portions. The heat exchange units are aligned, so that the plane portions are perpendicular to the flow direction of air which passes through the heat exchanger when the heat exchanger is installed.

Description: The present invention generally relates to a heat exchanger, such as a condenser or an evaporator, and more particularly, to heat exchangers including heat exchange units, at which an exchange of heat occurs, that have openings and louvers. A heat exchanger, such as an evaporator for use in an automotive air conditioning systems, is well known in the art. For example, such heat exchangers are described in US-A- 5 076 354 which forms the basis for the preamble of claim 1. In the known heat exchanger a plurality of corrugated fins are arranged between adjacent pipe portions. It is an object of the present invention to provide a lightweight heat exchanger with increased performance. A heat exchanger in accordance with the present invention includes a first tank and a second tank spaced vertically from the first tank. At least one connecting member extends between the first tank and the second tank. The at least one connecting member comprises a plurality of pipe portions, each having a longitudinal axis, which place the first tank and the second tank in fluid communication, and a plurality of plane portions one of which is fixedly disposed between each pair of adjacent pipe portions. The heat exchanger further comprises a plurality of openings formed at the plane portions along the longitudinal axis of the at least one connecting member. A plurality of louvers are formed at the openings, respectively, so that the louvers are parallel to a plane, which is perpendicular to the longitudinal axes of the pipe portions. The at least one connecting member is oriented, so that said plane portions are perpendicular to a flow direction of air which passes through the heat exchanger. The invention further includes a method of manufacturing a heat exchanger. The manufactured heat exchanger includes a first tank and a second tank spaced vertically from the first tank, and at least one connecting member which extends between the first tank to the second tank. The at least one connecting member comprises a plurality of pipe portions, each having a longitudinal axis, which place the first tank and the second tank in fluid communication, and a plurality of plane portions. Each of these plane portions are fixedly disposed between a pair of adjacent pipe portions. The method comprises the steps of forming a plurality of slits in the plane portions along the longitudinal axis of the at least one connecting member, so that the slits are perpendicular to the longitudinal axes of the pipe portions, thereby defining a plurality of plane belt regions between the adjacent slits; and twisting each of the plane belt regions, so that the plane belt regions are parallel with a plane perpendicular to the longitudinal axes of the pipe portions. Other objects, advantages, and features will be apparent when the detailed description and drawings are considered. For a more complete understanding of the present invention and the technical advantages thereof, reference is made to the following description taken in conjunction with accompanying drawings in which: Fig. 1 is a perspective view of an evaporator in accordance with a first embodiment of the present invention. Fig. 2 is a latitudinal cross-sectional view of the evaporator shown in Fig. 1 . Fig. 3 is an enlarged view of Fig. 2 . Figs. 4-9 are views illustrating a step of a method for manufacturing the heat exchange unit shown in Fig. 1 . Figs. 10-13 are views illustrating a method for manufacturing of the louvers shown in Fig. 1 . Figs. 14-16 are views illustrating an assembling process of the evaporator shown in Fig. 1 . Fig. 17 is a bottom view of the upper tank shown in Fig. 1 . Fig. 18 is a perspective view of a heat exchange unit of an evaporator in accordance with a second embodiment of the present invention. A heat exchanger in accordance with a first embodiment of the present invention is illustrated in Fig. 1 . In Fig. 1 , evaporator 10 includes an upper tank 11 and a lower tank 12 which is spaced vertically from the upper tank 11. Upper and lower tanks 11 and 12 may be made of an aluminum alloy and are rectangular parallelepiped in shape. Evaporator 10 further includes a plurality of heat exchange units 13 at which an exchange of heat occurs. Each of heat exchange units 13 also may be made of an aluminum alloy and includes a plurality of circular pipe portions 131 which are spaced from one another at about equal intervals and a plurality of plane portions 132 which extend between adjacent pipe portions 131. Referring to Figs. 4-9 , each heat exchange unit 13 may be formed by the following method. First, as illustrated in Figs. 4 and 5 , pipe portions 131 and plane portions 132 may be formed integrally as an aluminum alloy plate (not shown), for example, by extrusion. Then, an upper end section of each of plane portions 132 may be simultaneously cut out, for example, by press work Similarly, a lower end section of each of plane portions 132 may be simultaneously cut out, for example, by press work. Thus, partially formed heat exchange unit 13', as illustrated in Fig. 6 , may be prepared. Next, an upper end section of each of pipe portions 131 may be simultaneously tapered, for example, by drawing by means of a die 200, such as that illustrated in Figs. 7 and 8 . Die 200 may include a plurality of truncated cone-shaped hollow cavities 201 formed in one side surface thereof. A bottom end of each of truncated cone-shaped hollow cavities 201 may terminate at about the center of die 200. Each of truncated cone-shaped hollow cavities 201 may be tapered toward the bottom end thereof. Such hollow cavities 201 are spaced from one another at about equal intervals, so that they correspond to pipe portions 131 of heat exchange units 13. The upper end sections of each of pipe portions 131 may be simultaneously tapered, for example, by drawing. Similarly, the lower end sections of each of pipe portions 131 may be simultaneously tapered, for example, by drawing. Thus, heat exchange unit 13, such as that illustrated in Fig. 9 , may be obtained. Referring again to Fig. 1 , heat exchange units 13 may be arranged in parallel along the width w t of tanks 11 and 12 at about equal intervals, and may extend between upper and lower tanks 11 and 12. Upper and lower tanks 11 and 12 are placed in fluid communication through pipe portions 131 of heat exchange units 13. As illustrated in Fig. 2 , pipe portions 131 of adjacent heat exchange units 13 are arranged, such that they are offset by one half of the length of the interval of pipe portions 131 of heat exchange unit 13. Further, as illustrated in Fig. 3 , the thickness t pipe of the walls of pipe portions 131 is designed to be greater than the thickness t plane of plane portions 132, so that pipe portions 131 are reinforced to sufficiently resist the internal pressure. Referring to Figs. 10-13 in view of Fig. 1 , evaporator 10 is provided with a plurality of louvers 133 formed in plane portions 132 of heat exchange units 13. A method of forming louvers 133 is as follows. As illustrated in Fig. 10 , a plurality of slits 134 perpendicular to the longitudinal axis of pipe portions 131 are slit in each of plane portions 132 of heat exchange unit 13 along the longitudinal axis of heat exchange unit 13, for example, by press work. Slits 134 may be spaced from one another at about equal intervals W S . As shown in Fig. 10 , the lengths L S of each of slits 134 are about equal. Accordingly, a plurality of identical plane belt regions 134a may be defined between adjacent slits 134. As slits 134 are formed in plane portion 132, each of plane belt regions 134a is twisted to be parallel to a plane which is perpendicular to the longitudinal axis of pipe portions 131. The above slitting and twisting processes may be performed, for example, by only one step of press work As a result of twisting plane belt regions 134a, plane belt regions 134a are formed as louvers 133, and trapezoidal upper and lower openings 136 and 137 of louvers 133 are formed in plane portions 132, as illustrated in Figs. 11-13. Moreover, the length L L of a front edge of louvers 133 is about equal to the length L S of slits 134. Referring yet again to Fig. 1 , an interior space of the upper tank 11 is divided by partition plate 14 into a first chamber section 111 and a second chamber section 112. Upper tank 11 is provided with an inlet pipe 15 fixedly connected through an outside end surface of first chamber section 111 and an outlet pipe 16 fixedly connected through an outside end surface of second chamber section 112. Referring to Figs. 14-16 , evaporator 10 may be assembled by the following method. First, a plurality of rectangular plates 17 are prepared. Each of plates 17 comprises a plurality of circular holes 171 formed along the longitudinal axis thereof. The number of circular holes 171 is equal to the number of pipe portions 131 of heat exchange units 13. Circular holes 171 are spaced from one another at about equal intervals, so that holes 171 correspond to the positions of pipe portions 131 of heat exchange units 13. The inner diameter of each circular hole 171 is designed to be slightly greater than an outer diameter of pipe portion 131 of heat exchange unit 13. As indicated by arrows "B" in Fig. 14 , the upper end sections of pipe portions 131 are inserted into the corresponding circular holes 171 of a plate 17, so that plate 17 is disposed on the upper end sections of plane portions 132 of heat exchange units 13. Similarly, as indicated by arrows "C" in Fig. 14 , the lower end sections of pipe portions 131 are inserted into the corresponding circular holes 171 of another plate 17, so that the other plate 17 is disposed on the lower end sections of plane portions 132 of heat exchange units 13. Next, referring to Figs. 15 and 16 , four bars 18 having a substantially square lateral cross-section are provided. Each of bars 18 includes a slot 181 formed in a side surface thereof and having an end wall. Slot 181 extends along about the entire length of bar 18 and has a width which is slightly greater than the thickness of plate 17. One end portion of each of plates 17 that are disposed on the upper end of plane portions 132 of the corresponding heat exchange units 13 may be inserted into slot 181 of first bar 18 until one end portion of plate 17 contacts the end wall of slot 181 of first bar 18. The other end portion of each of plates 17 that are disposed on the upper end of plane portions 132 of the corresponding heat exchange units 13 may be inserted into slot 181 of second bar 18 until the other end portion of plate 17 contacts the end wall of slot 181 of second bar 18. Similarly, one end portion of each of plates 17 that are disposed on the lower end of plane portions 132 of the corresponding heat exchange units 13 may be inserted into slot 181 of third bar 18 until one end portion of plate 17 contacts the end wall of slot 181 of third bar 18. Finally, the other end portion of each of plates 17 that are disposed on the lower end of plane portions 132 of corresponding heat exchange units 13 may be inserted into slot 181 of fourth bar 18 until the other end portion of plate 17 contacts the end wall of slot 181 of fourth bar 18. The upper end sections of pipe portions 131 of each of heat exchange units 13 then may be inserted into the corresponding circular holes 11a, which are formed at a lower end surface of upper tank 11, as illustrated in Fig. 17 . In Fig. 17 , circular holes 11a are arranged to form a plurality of rows, e.g. , nine rows, which correspond to a plurality of, e.g. , nine, heat exchange units 13. In each row, holes 11a are spaced from one another at about equal intervals, so that holes 11a correspond pipe portions 131 of heat exchange units 13. Holes 11a of adjacent rows are offset by about one half of the length of the interval between holes 11a in each row. Similarly, the lower end sections of pipe portions 131 of each of heat exchange units 13 are inserted into the holes 12a, which are formed at the upper end surface of lower tank 12, as illustrated in Fig. 17 . Moreover, the inner diameter of holes 11a and 12a is designed to be slightly greater than the outer diameter of pipe portions 131 of heat exchange units 13. In addition, because the upper and lower end sections of pipe portions 131 of heat exchange units 13 are tapered, as illustrated in Fig. 9 , the upper and lower end sections of each of pipe portions 131 may be inserted into the holes 11a of upper tank 11 and holes 12a of lower tank 12, respectively, in a method of assembling evaporator 10. Four bars 18 aid in the assembly of evaporator 10. After evaporator 10 is assembled, four bars 18 may be detached and, assembled evaporator 10 may be placed in a brazing furnace for a sequential brazing process. Although none or only some of louvers 133 are illustrated in Figs. 1, 4-6 , 9, 14 , and 16 , louvers 133 are formed in each of plane portions 132 of each heat exchange units 13 and are arranged from the upper to lower ends of each plane portion 132. Moreover, as illustrated in Fig. 1 , when evaporator 10 is installed, heat exchange units 13 are oriented, so that plane portions 132 are aligned perpendicular to the flow direction, indicated by arrow "A," of air which passes through evaporator 10. Consequently, pipe portions 131 also are perpendicular to the flow direction "A" of air passing through evaporator 10. The flow direction of the air passing through evaporator 10 also is indicated by arrow "A" in Figs. 2-3, 11, 13 , and 17 . During operadon of the automotive air conditioning system, the refrigerant fluid is conducted into first chamber section 111 of upper tank 11 from an element of the automotive air conditioning system, such as a condenser (not shown), via inlet pipe 15. The refrigerant fluid conducted into first chamber section 111 of upper tank 11 flows downwardly through a first group of pipe portions 131 of heat exchange units 13. When the refrigerant fluid flows downwardly through the first group of pipe portions 131 of heat exchange units 13, the refrigerant exchanges heat with the air flowing across the exterior surfaces of heat exchange units 13, so that heat from the air is absorbed through plane portions 132. The refrigerant fluid flowing downwardly through the first group of pipe portions 131 of heat exchange units 13 flows into a first portion of an interior space of lower tank 12, which corresponds to first chamber section 111. Thereafter, the refrigerant fluid in the first portion of the interior space of lower tank 12 flows to a second portion of the interior space of lower tank 12, which corresponds to second chamber section 112, and then flows upwardly through a second group of pipe portions 131 of heat exchange units 13. When the refrigerant fluid flows upwardly through the second group of pipe portions 131 of heat exchange units 13, the refrigerant further exchanges heat with the air flowing across the exterior surfaces of heat exchange units 13, so that the heat from the air is further absorbed through plane portions 132. The refrigerant fluid flowing upwardly through the second group of pipe portions 131 of heat exchange units 13 nows into second chamber section 112 of upper tank 11. The refrigerant fluid in second chamber section 112 of upper tank 11 then is conducted to other elements of the automotive air conditioning system, such as a compressor (not shown), via outlet pipe 16. In a first embodiment of the present invention, the air passing through evaporator 10 is cut by the front edge of louvers 133 with an effective length ℓ, determined by equation (1): ℓ = L L - sin  Because heat exchange units 13 are oriented, so that plane portions 132 are aligned perpendicular to the flow direction, indicated by arrow "A," of air which passes through evaporator 10, angle theta  equals +90°. Therefore, the effective length ℓ of the front edge of louvers 133 equals L L , which is the maximum value thereof. As described above, with regard to louvers 133, the following relationships are observed: a. Angle  ∝ Effective Length ℓ; b. Effective Length ℓ ∝ Front Edge Effect; c. Front Edge Effect ∝ Heat Transfer Rate; and d. Heat Transfer Rate ∝ Performance of Evaporator. Accordingly, the performance of evaporator 10 increases. On the other hand, because angle , which is created between louvers 133 and a plane perpendicular to the longitudinal axes of pipe portions 131, is zero degrees, the length L L of louvers 133 is minimized under the condition where the interval between the adjacent pipe portions 131 of heat exchange unit 13 is fixed. Further, the length L L of louvers 133 is also about equal to the length L S of slits 134. Thus, as described above with regard to louvers 133, the following additional relationships are observed: a. Angle  ∝ Length L L ; b. 1/(Length L L ) ∝ Fin Efficiency; and c. Fin Efficiency ∝ Performance of Evaporator. Accordingly, the performance of evaporator 10 also increases. As described above, according to the first embodiment of the present invention, both the beat transfer rate, i.e. , the heat transfer coefficient, and the fin efficiency of louvers 133 increase, so that the performance of evaporator 10 increases. Further, according to this first embodiment, pipe portions 131 of adjacent heat exchange units 13 are arranged to be offset by one half of the length of the interval between adjacent pipe portions 131 of heat exchange units 13, as illustrated in Fig. 2 . Therefore, the air passing through evaporator 10 uniformly flows across the exterior surfaces of heat exchange units 13. As a result, the exchange of heat between the refrigerant and the air passing through evaporator 10 is effectively accomplished. In addition, according to the first embodiment of the present invention, plane portions 132 of heat exchange units 13 function substantially as fin members. Therefore, plane portions 132 may be thinned to the limits of the mechanical strength thereof. Thus, a lightweight evaporator may be obtained in addition to the other advantages described above. Fig. 18 illustrates one of a plurality of substantially identical heat exchange units 23 of a heat exchanger in accordance with a second embodiment of the present invention. Referring to Fig. 18 , heat exchange unit 23 includes a single thin plate member 231 of an aluminum alloy. A plurality of first arch portions 231a and a plurality of second arch portions (not shown) are bulged from the plane of plate member 231 alternately in opposite directions. First arch portions 231a and second arch portions (not shown) are aligned in a plurality of rows which extend parallel to the longitudinal axis of plate member 231. Moreover, first arch portions 231a and second arch portions (not shown) alternately follow one another in each of the rows, so that a plurality of substantially cylindrical passages 232 are formed in the plane of thin plate member 231. Plane region 231b is defined in thin plate member 231 between the adjacent substantially cylindrical passages 232. Heat exchange unit 23 further includes a plurality of pipe members 233 made of an aluminum alloy penetrating through the substantial cylindrical passages 232. The length of pipe members 233 is designed to be greater than the height of plate member 231. Therefore, when pipe members 233 are disposed in the corresponding substantially cylindrical passages 232, the ends of pipe members 233 project beyond the edges of plate member 231. A plurality of louvers 234, which are identical to louvers 133 as illustrated in Fig. 11 , are formed in plane regions 231b of plate member 231. However, no louver 234 is formed at least one outer plane region 231c because that the width of at least one outer plane region 231c of plate member 231 is designed to be narrower than that of the other plane regions 231b. The second embodiment achieves efficiencies substantially similar to those of the first embodiment.

Claims: A heat exchanger comprising: a first tank (11) and a second tank (12) spaced vertically from said first tank (11), and at least one connecting member (13;23) which extends between said first tank (11) and said second tank (12); said at least one connecting member (13;23) comprising a plurality of pipe portions (131,233), each having a longitudinal axis, which place said first tank (11) and said second tank (12) in fluid communication; characterized by: a plurality of plane portions (132,231b), one of which is fixedly disposed between each pair of adjacent pipe portions (131,233); a plurality of openings (136,137) formed in said plane portions (132,231b) and extending along a longitudinal axis of said at least one connecting member (13,23); and a plurality of louvers (133,234) formed at said openings (136,137), respectively, so that said louvers (133,234) are parallel to a plane which is perpendicular to the longitudinal axes of said pipe portions (131,233); wherein said at least one connecting member (13,23) is oriented, so that said plane portions (132,231b) are perpendicular to a flow direction (A) of air which passes through said heat exchanger. The heat exchanger of claim 1, characterized in that the at least one connecting member (13; 23) comprises a plurality of first arch portions (231a) and a plurality of second arch portions, the first and second arch portions being bulged in opposite directions and arranged in a plurality of rows to form a plurality of cylindrical passages (232), the pipe portions (233) extending through the cylindrical passages (232). The heat exchanger of claim 2, characterized in that the at least one connecting member (23) includes a single plate from which the plane portions (231b) and the first and second arch portions (231a) are formed. The heat exchanger of any of claims 1 to 3, characterized in that the upper and lower tanks (11, 12) are rectangular parallelepiped in shape. The heat exchanger of any of claims 1 to 4, characterized in that the at least one connecting member (13; 23) is made of aluminum alloy. The heat exchanger of any of claims 1 to 5, characterized in that each of the pipe portions (131; 233) has a circular cross-section. The heat exchanger of any of the claims 1 to 6, characterized in that the heat exchanger is an evaporator. A method of manufacturing a heat exchanger including a first tank (11) and a second tank (12) spaced vertically from the first tank, and at least one connecting member (13,23) which extends between the first tank and the second tank, the at least one connecting member comprising a plurality of pipe portions (131,233), each having a longitudinal axis, which place the first tank and the second tank in fluid communication, and a plurality of plane portions (132,231b), each of which is fixedly disposed between each pair of adjacent pipe portions, the method comprising the steps of forming a plurality of slits (134) in the plane portions spaced along the longitudinal axis of the at least one connecting member so that the slits are perpendicular to the longitudinal axis of the pipe portions, thereby defining a plurality of plane belt regions (134a) between adjacent slits, and twisting each of the plane belt regions so that the plane belt regions are parallel with a plane perpendicular to the longitudinal axis of the pipe portions. The method of claim 8, characterized in that the at least one connecting member (13,23) is made by providing a plurality of first arch portions (231a) and a plurality of second arch portions between adjacent plane portions (231b), the first and second arch portions being bulged in opposite directions and arranged in a plurality of rows to form a plurality of cylindrical passages (232), and that the pipe portions (233) are passed through the cylindrical passages. The method of claim 9, characterized in that the at least one connecting member (23) includes a single plate from which the plane portions (231b) and the first and second arch portions are formed.

Inventors: SASAKI KENICHI, SASAKI, KENICHI
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1994
Main classification: F28F3
IPC codes: F28F1, F28D1